Method for polishing a workpiece

ABSTRACT

A polishing apparatus can supply a polishing liquid uniformly and efficiently to a surface to be polished of a workpiece. The polishing apparatus includes a polishing table having a polishing surface, and a top ring for holding a semiconductor wafer and pressing the semiconductor wafer against the polishing surface. The polishing apparatus also includes a polishing liquid supply port for supplying a polishing liquid to the polishing surface, and a moving mechanism for moving the polishing liquid supply port to distribute the polishing liquid uniformly over an entire surface of the workpiece due to relative movement of the workpiece and the polishing surface.

This application is a divisional of application Ser. No. 11/086,420,filed Mar. 23, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing apparatus and a polishingmethod, and more particularly to a polishing apparatus and a polishingmethod for polishing a workpiece such as a semiconductor wafer or thelike to a flat finish.

The present invention also pertains to an interconnects forming method,and more particularly to an interconnects forming method for forminginterconnects in the form of a conductive film on a substrate such as asemiconductor wafer or the like.

2. Description of the Related Art

Recent rapid progress in semiconductor device integration demandssmaller and smaller wiring patterns or interconnects and also narrowerspaces between interconnects which connect active areas. One of theprocesses available for forming such interconnects is photolithography.Though a photolithographic process can form interconnects that are atmost 0.5 μm wide, it requires that surfaces on which pattern images areto be focused by a stepper be as flat as possible because depth of focusof an optical system is relatively small. It is therefore necessary tomake surfaces of semiconductor wafers flat for photolithography. Onecustomary way of flattening surfaces of semiconductor wafers is topolish them with a polishing apparatus, and such a process is calledChemical Mechanical Polishing (CMP).

A chemical-mechanical polishing (CMP) apparatus has a polishing tablewith a polishing pad disposed on its upper surface and a top ringpositioned above the polishing pad. A semiconductor wafer to be polishedis supported by the top ring and placed between the polishing pad andthe top ring. While a polishing liquid or slurry is being supplied tothe surface of the polishing pad, the top ring presses the semiconductorwafer against the polishing pad and rotates the semiconductor waferrelatively to the polishing pad, thereby polishing a surface of thesemiconductor wafer to a flat mirror finish.

Known chemical-mechanical polishing apparatus of the nature describedabove are disclosed in Japanese laid-open patent publication No.2002-113653, Japanese laid-open patent publication No. H10-58309,Japanese laid-open patent publication No. H10-286758, Japanese laid-openpatent publication No. 2003-133277, and Japanese laid-open patentpublication No. 2001-237208, for example.

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide a polishingapparatus which is capable of supplying a polishing liquid uniformly andefficiently to a surface to be polished of a workpiece.

A second object of the present invention is to provide a polishingapparatus which is capable of stably supplying a polishing liquidbetween a polishing surface and a workpiece to be polished.

A third object of the present invention is to provide a polishingapparatus which is capable of forming a uniform polishing liquid film ona polishing surface by holding a suitable amount of polishing liquid onthe polishing surface even under conditions in which polishing pressureon the polishing surface is low and relative speed between the polishingsurface and a workpiece is high.

A fourth object of the present invention is to provide a polishingapparatus which is capable of increasing an amount of polishing liquidheld on a polishing surface thereby to increase working efficiency ofthe polishing liquid.

A fifth object of the present invention is to provide a polishingapparatus and a polishing method which are capable of keeping apolishing surface clean at all times to stabilize polishingcharacteristics of a polishing surface.

A sixth object of the present invention is to provide a polishing methodwhich is capable of effectively washing away and removing residues suchas a polishing liquid attached to a surface to be polished of aworkpiece after the workpiece has been polished in a main polishingprocess.

A seventh object of the present invention is to provide a polishingmethod which is capable of preventing a previous polishing step fromposing an undue load on a subsequent polishing step in a multi-steppolishing process.

An eighth object of the present invention is to provide interconnectsforming method which is capable of forming interconnects without causingdefects therein.

According to a first aspect of the present invention, there is provideda polishing apparatus which is capable of supplying a polishing liquiduniformly and efficiently to a surface to be polished of a workpiece.The polishing apparatus includes a polishing table having a polishingsurface, and a top ring for holding a workpiece to be polished andpressing the workpiece against the polishing surface. The polishingapparatus also includes a polishing liquid supply port for supplying apolishing liquid to the polishing surface, and a moving mechanism formoving the polishing liquid supply port to distribute the polishingliquid uniformly over an entire surface of the workpiece due to relativemovement of the workpiece and the polishing surface.

The polishing liquid can uniformly and efficiently be supplied to thesurface to be polished of the workpiece by moving the polishing liquidsupply port while the workpiece is being polished. Specifically, sincethe polishing liquid supplied to the surface to be polished of theworkpiece is distributed uniformly, a polishing rate of the workpiece isimproved, and in-plane uniformity of the polishing rate is increased. Asthe polishing liquid is efficiently supplied, an amount of the polishingliquid used is reduced, and any wasteful consumption of the polishingliquid is reduced, thereby lowering a polishing cost.

According to a second aspect of the present invention, there is provideda polishing apparatus which is capable of supplying a polishing liquiduniformly and efficiently to a surface to be polished of a workpiece.The polishing apparatus includes a polishing table having a polishingsurface, and a top ring for holding a workpiece to be polished andpressing the workpiece against the polishing surface. The polishingapparatus also includes a plurality of polishing liquid supply ports forsupplying a polishing liquid to the polishing surface, and a liquid ratecontrol mechanism for controlling rates of the polishing liquid suppliedfrom the polishing liquid supply ports to distribute the polishingliquid uniformly over an entire surface of the workpiece due to relativemovement of the workpiece and the polishing surface.

The polishing liquid can uniformly and efficiently be supplied to thesurface to be polished of the workpiece by controlling the rates of thepolishing liquid supplied from the polishing liquid supply ports.Specifically, since the polishing liquid supplied to the surface to bepolished of the workpiece is distributed uniformly, a polishing rate ofthe workpiece is improved, and in-plane uniformity of the polishing rateis increased. As the polishing liquid is efficiently supplied, an amountof the polishing liquid used is reduced, and any wasteful consumption ofthe polishing liquid is reduced, thereby lowering a polishing cost.

According to a third aspect of the present invention, there is provideda polishing apparatus which is capable of supplying a polishing liquiduniformly and efficiently to a surface to be polished of a workpiece.The polishing apparatus includes a polishing table having a polishingsurface, and a top ring for holding a workpiece to be polished andpressing the workpiece against the polishing surface. The polishingapparatus also includes a distributor for distributing and supplying apolishing liquid to the polishing surface, and a polishing liquid supplyport for supplying the polishing liquid to the distributor.

Because the polishing liquid from the polishing liquid supply port isdistributed and supplied to the polishing surface, the polishing liquidsupplied to the surface to be polished of the workpiece is distributeduniformly. Therefore, a polishing rate of the workpiece is improved, andin-plane uniformity of the polishing rate is increased.

According to a fourth aspect of the present invention, there is provideda polishing apparatus which is capable of supplying a polishing liquiduniformly and efficiently to a surface to be polished of a workpiece.The polishing apparatus includes a polishing table having a polishingsurface, and a top ring for holding a workpiece to be polished andpressing the workpiece against the polishing surface. The polishingapparatus also includes a polishing liquid supply port for supplying apolishing liquid to the polishing surface, and a distributor fordistributing the polishing liquid supplied from the polishing liquidsupply port and supplying this distributed polishing liquid between theworkpiece and the polishing surface.

Inasmuch as the polishing liquid supplied from the polishing liquidsupply port can be distributed by the distributor, the polishing liquidsupplied to the surface to be polished of the workpiece is distributeduniformly. Therefore, a polishing rate of the workpiece is improved, andin-plane uniformity of the polishing rate is increased.

According to a fifth aspect of the present invention, there is provideda polishing apparatus which is capable of stably supplying a polishingliquid between a polishing surface and a workpiece to be polished. Thepolishing apparatus includes a polishing table having a polishingsurface, and a top ring for holding a workpiece to be polished andpressing the workpiece against the polishing surface. The top ring has aretainer ring for holding an outer circumferential edge of theworkpiece. The retainer ring, which comes into contact with thepolishing surface, has a groove defined in a surface thereof, with thegroove extending between outer and inner circumferential surfaces of theretainer ring. The groove has an opening ratio ranging from 10% to 50%at the outer circumferential surface of the retainer ring.

The groove defined in the retainer ring and extending between outer andinner circumferential surfaces of the retainer ring is able to stablysupply the polishing liquid between the polishing surface and theworkpiece. With the opening ratio of the groove being in the range from10% to 50% at the outer circumferential surface of the retainer ring,the polishing liquid can effectively be supplied between the polishingsurface and the workpiece, so that a stable polishing rate is achieved,and any inactive polishing liquid after it has reacted can be dischargedeffectively outside of the retainer ring through the groove.

According to a sixth aspect of the present invention, there is provideda polishing apparatus which is capable of forming a uniform polishingliquid film on a polishing surface by holding a suitable amount ofpolishing liquid on the polishing surface even under conditions in whichpolishing pressure on the polishing surface is low and relative speedbetween the polishing surface and a workpiece to be polished is high.The polishing apparatus includes a polishing table having a polishingsurface, and a top ring for holding a workpiece to be polished andpressing the workpiece against the polishing surface. The polishingapparatus also includes a polishing liquid supply port for supplying apolishing liquid to the polishing surface, and a relatively movingmechanism for moving the polishing surface and the workpiece relativelyto each other at a relative speed of at least 2 m/s. The polishingsurface has a groove having a cross-sectional area of at least 0.38 mm².

As the groove with this large cross-sectional area is defined in thepolishing surface, a uniform polishing liquid film can be formed on thepolishing surface by holding a suitable amount of polishing liquid onthe polishing surface even under conditions in which the polishingpressure on the polishing surface is low and the relative speed betweenthe polishing surface and the workpiece is high.

According to a seventh aspect of the present invention, there isprovided a polishing apparatus which is capable of increasing an amountof polishing liquid held on a polishing surface thereby to increase aworking efficiency of the polishing liquid. The polishing apparatusincludes a polishing table having a polishing surface, a top ring forholding a workpiece to be polished and pressing the workpiece againstthe polishing surface, and a polishing liquid supply port for supplyinga polishing liquid to the polishing surface. The polishing surface has aplurality of holes defined therein and each having an opening area of atleast 2.98 mm².

Since these plural holes each having a large opening area are defined inthe polishing surface, an amount of polishing liquid held on thepolishing surface is increased, and a working efficiency of thepolishing liquid is increased. Therefore, an amount of the polishingliquid used is reduced, and a polishing cost is lowered.

According to an eighth aspect of the present invention, there isprovided a polishing apparatus which is capable of supplying a polishingliquid uniformly to a surface to be polished of a workpiece. Thepolishing apparatus includes a polishing table having a polishingsurface, and a plurality of polishing liquid supply ports for supplyinga polishing liquid to the polishing surface. The polishing apparatusalso includes a plurality of polishing liquid supply lines extendingrespectively from the polishing liquid supply ports and adapted to beconnected directly to a polishing liquid circulation system which isdisposed outside of the polishing apparatus.

With the above arrangement, the workpiece can uniformly be supplied withthe polishing liquid. Therefore, a polishing rate of the workpiece isimproved, and in-plane uniformity of the polishing rate is increased.

According to a ninth aspect of the present invention, there is provideda polishing apparatus which is capable of keeping a polishing surfaceclean at all times to stabilize polishing characteristics of thepolishing surface. The polishing apparatus includes a polishing tablehaving a polishing surface, a top ring for holding a workpiece to bepolished and pressing the workpiece against the polishing surface, and afluid ejecting mechanism for ejecting a mixed fluid of a cleaning liquidand a gas to the polishing surface. The polishing apparatus alsoincludes a discharging mechanism for discharging the mixed fluid fromthe polishing surface, with the discharging mechanism being disposeddownstream of the fluid ejecting mechanism with respect to a directionin which the polishing surface moves.

The discharging mechanism can immediately discharge the cleaning liquidfrom the fluid ejecting mechanism out of the polishing surface, therebykeeping the polishing surface clean at all times. Therefore, thepolishing characteristics of the polishing apparatus can be stabilized,making it possible for the fluid ejecting mechanism to perform in-situatomizing while the workpiece is being polished.

According to a tenth aspect of the present invention, there is provideda polishing method which is capable of keeping a polishing surface cleanat all times to stabilize polishing characteristics of the polishingsurface. According to the polishing method, a workpiece is pressedagainst a polishing surface of a polishing table and polished by movingthe polishing surface and the workpiece relatively to each other. Amixed fluid of a cleaning liquid and a gas is ejected from a fluidejecting mechanism to the polishing surface while the workpiece is beingpolished. The mixed fluid is discharged from the polishing surface witha discharging mechanism which is disposed downstream of the fluidejecting mechanism with respect to a direction in which the polishingsurface moves.

In the above polishing method, the discharging mechanism can immediatelydischarge the cleaning liquid supplied by the fluid ejecting mechanism,from the polishing surface, thereby keeping the polishing surface cleanat all times. Therefore, the polishing characteristics of the polishingapparatus can be stabilized, making it possible for the fluid ejectingmechanism to perform in-situ atomizing while the workpiece is beingpolished.

According to an eleventh aspect of the present invention, there isprovided a polishing method which is capable of effectively washing awayand removing residues such as a polishing liquid attached to a surfaceto be polished of a workpiece after the workpiece has been polished in amain polishing process. According to the polishing method, the workpieceis polished under a low pressure of at most 13.79 kPa, and, thereafter,the workpiece is polished under a low pressure of at most 13.79 kPa at arelative speed of at least 2 m/s. between the workpiece and thepolishing surface while water is being supplied to the workpiece.

With the above polishing method, after the workpiece is polished under alow pressure, residues such as a polishing liquid attached to thesurface to be polished of the workpiece can effectively be washed awayand removed.

According to a twelfth aspect of the present invention, there isprovided a polishing method which is capable of effectively washing awayand removing residues such as a polishing liquid attached to a surfaceto be polished of a workpiece after the workpiece has been polished in amain polishing process. According to the polishing method, the workpieceis polished under a low pressure of at most 13.79 kPa, and, thereafter,the workpiece is polished under a low pressure of at most 13.79 kPa at arelative speed of at least 2 m/s. between the workpiece and thepolishing surface while a chemical solution is being supplied to theworkpiece.

With the above polishing method, after the workpiece is polished under alow pressure, residues such as a polishing liquid attached to thesurface to be polished of the workpiece can effectively washed away andremoved.

According to a thirteenth aspect of the present invention, there isprovided a polishing method which is capable of preventing a previouspolishing step from posing an undue load on a subsequent polishing stepin a multi-step polishing process, particularly a two-step polishingprocess. The polishing method includes polishing the workpiece to removea substantial portion of a first film formed on the workpiece in afirst-stage, and polishing the workpiece to remove a remaining portionof the first film until a second film on the workpiece is exposed in asecond-stage, thereby leaving an interconnect area. The polishing methodalso includes presetting a film thickness distribution for the firstfilm upon transition from the first-stage polishing to the second-stagepolishing, measuring a thickness of the first film with an eddy-currentsensor in the first-stage polishing to acquire a film thicknessdistribution of the first film, and adjusting polishing conditions inthe second-stage polishing to equalize the acquired film thicknessdistribution of the first film to the preset film thickness distributionfor the first film.

The above polishing method makes it possible to reliably achieve afinally desirable film thickness distribution while monitoring an actualfilm thickness distribution. Since the first-stage polishing can beswitched to the second-stage polishing at a desired film thicknessdistribution at all times, the first-stage polishing is prevented fromimposing an undue load on the second-stage polishing. Furthermore, thepolishing method is capable of preventing dishing and erosion fromoccurring after the second-stage polishing, and of reducing a period oftime spent by the second-stage polishing, resulting in an increase inproductivity and a reduction in polishing cost.

According to a fourteenth aspect of the present invention, there isprovided an interconnects forming method which is capable of forminginterconnects without causing defects therein. The interconnects formingmethod includes forming a flat conductive thin film on a substrate, andremoving the flat conductive thin film from the substrate by a chemicaletching process.

After the flat conductive thin film is formed on the substrate, theconductive thin film is removed by the chemical etching process which isfree of any mechanical action and does not require an electricconnection. Therefore, interconnects can be formed on the substratewithout causing defects.

According to the first through fourth aspects of the present invention,the polishing liquid can be supplied uniformly and efficiently to thesurface to be polished of the workpiece.

According to the fifth aspect of the present invention, the polishingliquid can stably be supplied between the polishing surface and theworkpiece.

According to the sixth aspect of the present invention, the uniformpolishing liquid film can be formed on the polishing surface by holdinga suitable amount of polishing liquid on the polishing surface evenunder conditions in which the polishing pressure on the polishingsurface is low and the relative speed between the polishing surface andthe workpiece is high.

According to the seventh aspect of the present invention, the amount ofpolishing liquid held on the polishing surface can be increased, therebyto increase a working efficiency of the polishing liquid.

According to the eighth aspect of the present invention, the polishingliquid can be supplied uniformly to the workpiece.

According to the ninth and tenth aspects of the present invention, thepolishing surface is kept clean at all times to stabilize the polishingcharacteristics of the polishing surface.

According to the eleventh and twelfth aspects of the present invention,residues such as a polishing liquid attached to the surface to bepolished of the workpiece after the workpiece has been polished in themain polishing process can effectively be washed away and removed.

According to the thirteenth aspect of the present invention, a previouspolishing step is prevented from posing an undue load on a subsequentpolishing step in a multi-step polishing process.

According to the fourteenth aspect of the present invention,interconnects can be formed without causing defects therein.

The above and other objects, features, and advantages of the presentinvention will become apparent from the following description when takenin conjunction with the accompanying drawings which illustrate preferredembodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a polishing apparatus according to anembodiment of the present invention;

FIG. 2 is a vertical cross-sectional view of a portion of a polishingunit of the polishing apparatus shown in FIG. 1;

FIG. 3 is a bottom view of a retainer ring of a top ring shown in FIG.2;

FIG. 4 is a bottom view of another retainer ring for use with the topring shown in FIG. 2;

FIG. 5 is a bottom view of still another retainer ring for use with thetop ring shown in FIG. 2;

FIG. 6 is a bottom view of still another retainer ring for use with thetop ring shown in FIG. 2;

FIG. 7 is a schematic plan view of the polishing unit of the polishingapparatus shown in FIG. 1;

FIG. 8 is a perspective view of a gas ejecting mechanism used in thepolishing unit shown in FIG. 7;

FIG. 9 is a plan view of a modified polishing unit for use in thepolishing apparatus shown in FIG. 1;

FIG. 10 is a perspective view of a polishing pad of the polishing unitshown in FIG. 7;

FIG. 11 is an enlarged vertical cross-sectional view of the polishingpad shown in FIG. 10;

FIG. 12 is an enlarged plan view of a modification of the polishing padshown in FIG. 10;

FIG. 13 is a plan view of a modification of the polishing unit of thepolishing apparatus shown in FIG. 1;

FIG. 14 is a plan view of another modification of the polishing unit ofthe polishing apparatus shown in FIG. 1;

FIG. 15 is a plan view of still another modification of the polishingunit of the polishing apparatus shown in FIG. 1;

FIG. 16 is a plan view of still another modification of the polishingunit of the polishing apparatus shown in FIG. 1;

FIG. 17 is a plan view of still another modification of the polishingunit of the polishing apparatus shown in FIG. 1;

FIG. 18 is a plan view of still another modification of the polishingunit of the polishing apparatus shown in FIG. 1;

FIG. 19 is a plan view of still another modification of the polishingunit of the polishing apparatus shown in FIG. 1;

FIG. 20 is a plan view of still another modification of the polishingunit of the polishing apparatus shown in FIG. 1;

FIG. 21 is a perspective view of a modified polishing liquid supplynozzle for use in the polishing unit of the polishing apparatus shown inFIG. 1;

FIG. 22 is a vertical cross-sectional view of the polishing liquidsupply nozzle shown in FIG. 21;

FIG. 23 is a perspective view of a modification of the polishing liquidsupply nozzle shown in FIG. 21;

FIG. 24 is a perspective view of another modified polishing liquidsupply nozzle for use in the polishing unit of the polishing apparatusshown in FIG. 1;

FIG. 25 is a perspective view of another modification of the polishingliquid supply nozzle shown in FIG. 21;

FIG. 26 is a perspective view of still another modified polishing liquidsupply nozzle for use in the polishing unit of the polishing apparatusshown in FIG. 1;

FIG. 27 is a plan view of still another modified polishing liquid supplynozzle for use in the polishing unit of the polishing apparatus shown inFIG. 1;

FIG. 28 is a schematic view of still another modified polishing liquidsupply nozzle for use in the polishing unit of the polishing apparatusshown in FIG. 1;

FIG. 29 is a schematic view of a polishing liquid supply system of aconventional polishing apparatus;

FIG. 30 is a schematic view of a polishing liquid supply systemaccording to the present invention;

FIGS. 31A and 31B are schematic views of fluid pressure valves for usein the polishing liquid supply system shown in FIG. 30;

FIG. 32 is a vertical cross-sectional view of a modification of the topring shown in FIG. 2;

FIGS. 33A through 33C are cross-sectional views illustrative of a CMPprocess of planarizing copper damascene interconnects;

FIG. 34A is a cross-sectional view of an overpolished workpiece, andFIG. 34B is a cross-sectional view of an underpolished workpiece;

FIG. 35 is a plan view of a polishing apparatus for polishing asemiconductor wafer with a swingable polishing liquid supply nozzle; and

FIG. 36A is a graph showing a polishing rate of the semiconductor waferwhich is polished by the polishing apparatus shown in FIG. 35 when thepolishing liquid supply nozzle swings, while FIG. 36B is a graph showinga polishing rate of the semiconductor wafer which is polished by thepolishing apparatus shown in FIG. 35 when the polishing liquid supplynozzle does not swing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A polishing apparatus according to an embodiment of the presentinvention will be described below with references to the drawings. Inthe drawings, like or corresponding parts are denoted by like orcorresponding reference characters throughout views and will not bedescribed repetitively.

FIG. 1 shows in plan a polishing apparatus according to an embodiment ofthe present invention. As shown in FIG. 1, the polishing apparatus hasan array of three wafer cassettes 10 removably mounted on an end wallthereof for holding semiconductor wafers, and a traveling mechanism 12disposed along the array of three wafer cassettes 10. A first transferrobot 14 is mounted on the traveling mechanism 12 and has two hands forselectively accessing the wafer cassettes 10.

The polishing apparatus has an array of four polishing units 20 arrangedin a longitudinal direction thereof. Each of the polishing units 20includes a polishing table 22 having a polishing surface, a top ring 24for holding and pressing a semiconductor wafer against the polishingsurface of the polishing table 22 to polish the semiconductor wafer, apolishing liquid supply nozzle 26 for supplying a polishing liquid and adressing liquid (e.g., water) to the polishing surface of the polishingtable 22, a dresser 28 for dressing the polishing surface, and anatomizer 30 for atomizing a mixed fluid composed of a liquid (e.g., purewater) and a gas (e.g., nitrogen) and ejecting this atomized fluid fromat least one nozzle to the polishing surface.

A first linear transporter 32 and a second linear transporter 34 aredisposed end to end alongside of the polishing units 20 for transportingsemiconductor wafers in a longitudinal direction of the polishingapparatus along the array of polishing units 20. A reversing machine 36for reversing a semiconductor wafer received from the first transferrobot 14 is disposed at an end of the first linear transporter 32 whichis closer to the wafer cassettes 10.

The polishing apparatus also has a second transfer robot 38, a reversingmachine 40 for reversing a semiconductor wafer received from the secondtransfer robot 38, an array of four cleaning machines 42 for cleaningpolished semiconductor wafers, and a transfer unit 44 for transferringsemiconductor wafers between the reversing machine 40 and the cleaningmachines 42. The second transfer robot 38, the reversing machine 40, andthe cleaning machines 42 are arrayed linearly in the longitudinaldirection of the polishing apparatus on one side thereof.

Semiconductor wafers housed in the wafer cassettes 10 are introducedinto respective polishing units 20 through the reversing machine 36, thefirst linear transporter 32, and the second linear transporter 34. Thesemiconductor wafers are polished in each of polishing units 20. Thesepolished semiconductor wafers are then introduced into the cleaningmachines 42 through the second transfer robot 38 and the reversingmachine 40, and cleaned by respective cleaning machines 42. Thesecleaned semiconductor wafers are then delivered by the first transferrobot 14 back into the wafer cassettes 10.

FIG. 2 shows in vertical cross section a portion of each of thepolishing units 20. As shown in FIG. 2, the polishing table 22 of thepolishing unit 20 is connected to a motor 50 disposed therebeneath forrotation about its own axis in a direction indicated by an arrow. Apolishing pad (polishing cloth) 52 having an upper polishing surface isapplied to an upper surface of the polishing table 22. The top ring 24is coupled to a lower end of a vertical top ring shaft 54. A retainerring 56 for holding an outer circumferential edge of a semiconductorwafer W is mounted on an outer circumferential surface of a lowerportion of the top ring 24.

The top ring shaft 54 is coupled at its upper end to a motor (not shown)and also to a lifting/lowering cylinder (not shown). The top ring 24 istherefore vertically movable and rotatable about its own axis asindicated by arrows for pressing the semiconductor wafer W against thepolishing pad 52 under desired pressure and rotating the semiconductorwafer W with respect to the polishing pad 52.

In operation of the polishing unit 20, the semiconductor wafer W is heldon a lower surface of the top ring 24, and pressed by thelifting/lowering cylinder against the polishing pad 52 on the polishingtable 22 which is being rotated by the motor 50. A polishing liquid Q issupplied from a polishing liquid supply port 57 of the polishing liquidsupply nozzle 26 onto the polishing pad 52. The semiconductor wafer W isnow polished with the polishing liquid Q which is present between alower surface, to be polished, of the semiconductor wafer W and thepolishing pad 52.

As shown in FIG. 2, an eddy-current sensor 58 for measuring a filmthickness of the semiconductor wafer W is embedded in the polishingtable 22. A wire 60 extends from the eddy-current sensor 58 through thepolishing table 22 and a support shaft 62 connected to a lower endthereof, and is connected to a controller 66 through a rotary connector(or a slip ring) 64 that is mounted on a lower end of the support shaft62. While the eddy-current sensor 58 is moving beneath the semiconductorwafer W, the eddy-current sensor 58 detects the thickness of aconductive film, such as a copper film or the like, formed on thesurface of the semiconductor wafer W continuously along a path of theeddy-current sensor 58 beneath the semiconductor wafer W.

To meet demands for higher-speed semiconductor devices, it has beenstudied to make an insulating film between interconnects insemiconductor devices of a material having a lower dielectric constant,e.g., a low-k material. Since a material having a lower dielectricconstant, e.g., a low-k material, is porous and brittle mechanically, itis requested to minimize pressure (polishing pressure) applied to thesemiconductor wafer being polished to a level of at most 13.79 kPa (2psi), for example, in a polishing process of planarizing copperdamascene interconnects of low-k material.

Generally, however, a polishing rate in a polishing process depends uponpolishing pressure, and decreases as the polishing pressure is lowered.For polishing a copper film, therefore, a polishing liquid with astronger chemical action may be used to compensate for a reduction inthe polishing pressure. When such a polishing liquid with a strongerchemical action is used, uniform and stable polishing characteristicscannot be achieved unless a stabler chemical reaction occurs between thepolishing liquid and the copper film. Consequently, it is desired in apolishing process using a polishing liquid with a stronger chemicalaction to stably supply an unreacted polishing liquid between thepolishing pad and the semiconductor wafer.

According to this embodiment, the retainer ring 56 of the top ring 24has grooves defined therein for more stably supplying the polishingliquid between the polishing pad 52 and the semiconductor wafer W. FIG.3 is a bottom view of the retainer ring 56 shown in FIG. 2. As shown inFIG. 3, the retainer ring 56 has a plurality of grooves 74 defined in abottom surface thereof at equal circumferential intervals and extendingbetween an outer circumferential surface 70 and an inner circumferentialsurface 72 thereof. In FIG. 3, the top ring 24 rotates clockwise, andeach of the grooves 74 has an outer circumferential opening 76positioned ahead of an inner circumferential opening 78 thereofclockwise, i.e., in a direction in which the top ring 24 rotates. Thegrooves 74 thus defined in the retainer ring 56 are effective inefficiently and stably supplying polishing liquid between thesemiconductor wafer W positioned inside of the retainer ring 56 and thepolishing pad 52.

Outer circumferential openings 76 of the grooves 74 have an openingpercentage ranging from about 10% to about 50% with respect to a surfacearea of the outer circumferential surface 70, depending on intensity ofa chemical action of the polishing liquid. For example, when a certainpolishing liquid is used, if the opening percentage of the outercircumferential openings 76 is 0%, then the polishing liquid cannotsufficiently be supplied between the polishing pad 52 and thesemiconductor wafer W, thereby failing to achieve a sufficient polishingrate. If the opening percentage of the outer circumferential openings 76is excessively high, e.g., exceeds 50%, on the other hand, thenpolishing liquid that has flowed through some grooves 74 radiallyinwardly of the retainer ring 56 tend to flow out through other grooves74, and cannot effectively be retained between the polishing pad 52 andthe semiconductor wafer W. If the opening percentage of the outercircumferential openings 76 is selected in the range from about 10% toabout 50%, then the polishing liquid can effectively be supplied betweenthe polishing pad 52 and the semiconductor wafer W for a stablepolishing rate. The opening percentage of the outer circumferentialopenings 76, which is selected in the range from about 10% to about 50%,allows inactive polishing liquid after it has reacted to be dischargedeffectively outside of the retainer ring 56 through the grooves 74.Dimensions of the grooves 74 and a pitch between the grooves 74 aredetermined depending on the opening percentage of the outercircumferential openings 76.

If the top ring 24 rotates counterclockwise as viewed from its bottomsurface, then the grooves 74 should be oriented in a direction oppositeto the grooves 74 shown in FIG. 3, as shown in FIG. 4. Alternatively, asshown in FIG. 5, the grooves 74 may be disposed radially at equalcircumferential spaced intervals so that the grooves 74 may be usedirrespectively of which direction the top ring 24 may rotate. As shownin FIG. 6, the radial grooves 74 may have inner circumferential openings78 greater than outer circumferential openings 76 thereof.

For making the grooves 74 of the retainer ring 56 more effective, arotational speed of the top ring 24 should preferably be equal to orlower than a rotational speed of the polishing table 22, or morepreferably be about ⅓ through about 1/1.5 of the rotational speed of thepolishing table 22. The polishing table 22 and the top ring 24 may berotated in one direction or in opposite directions. If the rotationalspeeds of the polishing table 22 and the top ring 24 are set to theabove relative values, then the polishing apparatus can polish thesemiconductor wafer W more uniformly.

Specifically, if the rotational speed of the top ring 24 is higher thanthe rotational speed of the polishing table 22, then the retainer ring56 positioned on an outer circumferential surface of the top ring 24tends to obstruct an inflow of polishing liquid between the polishingpad 52 and the semiconductor wafer W, thereby preventing the polishingliquid from being efficiently supplied. If the rotational speed of thetop ring 24 is equal to or lower than the rotational speed of thepolishing table 22, then the polishing liquid can efficiently besupplied through the grooves 74 between the polishing pad 52 and thesemiconductor wafer W, thereby allowing the polishing apparatus topolish the semiconductor wafer W more uniformly.

FIG. 7 shows in schematic plan each of the polishing units 20 of thepolishing apparatus shown in FIG. 1. As shown in FIG. 7, the atomizer 30is disposed upstream of the top ring 24 with respect to a direction inwhich the polishing table 22 rotates. The atomizer 30 functions as afluid ejecting mechanism for ejecting a mixed fluid composed of acleaning liquid and a gas to the polishing pad 52. For example, a mixedfluid composed of a nitrogen gas and pure water or a chemical liquid isejected from the atomizer 30 to the polishing pad 52. The mixed fluid isejected as 1) fine liquid particles, 2) fine solidified liquidparticles, or 3) liquid-evaporated gas particles (these phases may bereferred to as a “nebulized or atomized” state) to the polishing pad 52.

When this nebulized or atomized mixed fluid is ejected to the polishingpad 52, any polishing liquid and swarf trapped in recesses in thepolishing pad 52 are lifted therefrom by the gas contained in the mixedfluid, and are washed away by a cleaning liquid such as pure water, achemical liquid, or the like. In this manner, any polishing liquid andswarf, which may be present on the polishing pad 52 and responsible fora scratch on the semiconductor wafer W, can effectively be removed.

After a semiconductor wafer is polished by a CMP process, polishingresidues including remaining abrasive grains and swarf (copper complexif a copper film is polished) are generally present on a polishedsurface of a semiconductor wafer. If these polishing residues remainunremoved, they tend to damage the polished surface of the semiconductorwafer or suppress a chemical reaction of a polishing liquid in asubsequent polishing process to reduce a polishing rate. It is thereforedesirable that no or little polishing residues be present on a surfacebeing polished of a semiconductor wafer. According to a normal CMPprocess, in an interval between polishing cycles, dressing of thepolishing surface is performed by a dresser, and an atomized mixed fluidcomposed of a cleaning liquid and a gas is applied from an atomizer tothe polishing surface to remove polishing residues from the polishingsurface. This process will be referred to as “atomizing process”.

As shown in FIG. 7, a draining mechanism 80 for draining mixed fluidejected from the atomizer 30 off the polishing pad 52 is disposeddownstream of the atomizer 30 with respect to the direction in which thepolishing table 22 rotates. A cover 82 covering the atomizer 30 and thedraining mechanism 80 is disposed above the atomizer 30 and the drainingmechanism 80. The cover 82 should preferably be made of a waterrepelling material such as fluororesin or the like. The cover 82 may beopen in a radial direction of the polishing table 22.

The draining mechanism 80 shown in FIG. 7 comprises a contact member 84for being brought into contact with the polishing pad 52, and a holder(not shown) that holds the contact member 84. The contact member 84should preferably be made of a material having a low coefficient offriction for smaller wear and also having a high liquid sealingcapability. The draining mechanism 80 may include a pressure-adjustablepressing mechanism (not shown) for pressing the contact member 84 or theholder under controlled pressure, and the contact member 84 may bebrought into contact with the polishing pad 52 under pressure from thepressing mechanism. The pressing mechanism may be a cylinder mechanismfor applying a fluid pressure such as a pneumatic or hydraulic pressure,or a ball screw mechanism.

According to the conventional CMP process, it has been customary not toperform the atomizing process, i.e., to apply atomized fluid to thepolishing surface, during polishing cycles because cleaning liquidsupplied to the polishing surface changes a concentration of a polishingliquid, thereby changing a polishing capability of the polishing liquid.According to this embodiment, since the draining mechanism 80 canimmediately drain the cleaning liquid supplied from the atomizer 30 offthe polishing table 22, the polishing pad 52 can be kept clean at alltimes, thereby stabilizing polishing characteristics of the polishingapparatus. Therefore, the polishing apparatus according to thisembodiment makes it possible for the atomizer 30 to perform theatomizing process (In-site atomizing process) during a polishing cycle.

A dressing process performed by the dresser 28 in a polishing cycle(In-site dressing process) and the atomizing process performed by theatomizer 30 in the polishing cycle (In-site atomizing process) may becombined with each other for conditioning the polishing pad 52 in thepolishing cycle. Accordingly, intervals between polishing cycles can bereduced for allowing the polishing apparatus to have an increasedthroughput.

According to an example shown in FIG. 7, the contact member 84 extendsin a radial direction of the polishing table 22. However, the contactmember 84 may be inclined a certain angle ranging from 0° to 90° from aradial direction of the polishing table 22.

The polishing unit 20 may have a gas ejecting mechanism having gasejection ports for ejecting a gas to the polishing pad 52, instead of orin addition to the contact member 84. FIG. 8 shows in perspective such agas ejecting mechanism 86. As shown in FIG. 8, the gas ejectingmechanism 86 has a plurality of gas ejection ports 88 for ejecting agas, such as dry air or dry nitrogen, to the polishing pad 52, and acontroller (not shown) for controlling an ejected amount of gas,pressure at which the gas is ejected, and a direction in which the gasis ejected. The cleaning liquid from the atomizer 30 is drained off thepolishing pad 52 by the gas ejected from the gas ejection ports 88. Thegas ejection ports 88 should preferably be shaped to eject the gas in asectoral pattern like an air curtain. The gas ejection ports 88 may bein the form of slits for controlling the direction in which the gas isejected.

The draining mechanism 80, which is combined with the gas ejectingmechanism 86, is also capable of immediately draining the cleaningliquid supplied from the atomizer 30 off the polishing pad 52.Accordingly, the polishing pad 52 can be kept clean at all times so asto stabilize polishing characteristics of the polishing apparatus.

Efforts are being made to produce higher-performance LSI circuits byemploying finer interconnects to have them operate at higher speeds,allow them to be integrated more highly, and design them for lower powerconsumption. Technological development for finer interconnects has beenperformed essentially according to predictions based on theInternational Technology Roadmap for Semiconductors (ITRS). Developingfiner interconnects has been paralleled by converting interconnectmaterials into copper having lower resistance and insulating materialsinto low-k materials having low dielectric constants. It is expectedthat there will be growing demands for a copper damascene planarizingprocess (copper CMP process).

For achieving integration with low-k materials or porous low-k materialsin the copper damascene planarizing process, it is necessary to improveplanarizing characteristics with efforts to produce finer interconnectsand also to take some countermeasures against material breakdown uponpolishing due to low mechanical strength of these materials.

To meet the above requirements, it may be proposed to lower pressure ona surface being processed, i.e., polishing pressure. According to anordinary copper CMP process, after a copper complex is formed, thecopper complex is mechanically removed to polish a copper filmprogressively. With a polishing liquid that is used by the ordinary CMPapparatus, however, mechanical strength of this formed copper complex isso high that reducing the polishing pressure tends to result in areduction in a polishing rate.

Recently, there has been developed a polishing liquid for forming acopper complex having such a low mechanical strength that the coppercomplex can mechanically be removed under a low polishing pressure.Because such a polishing liquid is of strong chemical reactivity, anamount and distribution of the polishing liquid supplied to a surfacebeing polished of a semiconductor wafer greatly affects a polishing rateand in-plane uniformity of the polishing rate.

With a conventional CMP apparatus, as polishing liquid is supplied froma fixed single polishing liquid supply port, the polishing liquidsupplied therefrom to a surface being polished of a semiconductor waferis liable to have a localized distribution, thereby impairing in-planeuniformity of a polishing rate. This problem manifests itselfparticularly when a relative speed between a polishing surface and thesemiconductor wafer is high. In addition, an increased amount ofpolishing liquid is wasted, resulting in an increase in polishing cost.Accordingly, it is important that the surface being polished of thesemiconductor wafer be uniformly and efficiently supplied with thepolishing liquid.

According to this embodiment, the polishing liquid supply port 57 (seeFIG. 2) of the polishing liquid supply nozzle 26 is moved during apolishing process to supply the surface being polished of thesemiconductor wafer with the polishing liquid uniformly and efficiently.Specifically, as shown in FIG. 1, the polishing liquid supply nozzle 26of this embodiment can be pivoted about a shaft 27, and is pivoted aboutthe shaft 27 by a pivoting mechanism (moving mechanism) during thepolishing process.

The polishing liquid is supplied from the polishing liquid supply nozzle26 to the polishing pad 52. As the top ring 24 and the polishing table22 move relatively to each other, the polishing liquid supplied to thepolishing pad 52 is supplied to the surface being polished of thesemiconductor wafer. When the polishing liquid supply nozzle 26 ispivoted about the shaft 27 to move the polishing liquid supply port 57(see FIG. 2) mounted on its tip during the polishing process, thepolishing liquid supplied to the polishing pad 52 is appropriatelydistributed over the polishing pad 52 so as to be supplied uniformly toan entire surface of the semiconductor wafer as the top ring 24 and thepolishing table 22 move relatively to each other.

As described above, the polishing liquid supply nozzle 26 according tothis embodiment is capable of uniformizing distribution of the polishingliquid supplied to the surface being polished of the semiconductorwafer. Consequently, the polishing rate is improved, and the in-planeuniformity of the polishing is increased. As the polishing liquid isefficiently supplied, an amount of the polishing liquid used is reduced,and any wasteful consumption of the polishing liquid is reduced, therebylowering the polishing cost.

In this embodiment, the polishing liquid supply nozzle 26 is pivotedalong an arcuate path. However, the polishing liquid supply nozzle 26may be moved according to other patterns. For example, the polishingliquid supply nozzle 26 may be moved linearly, rotated, swung, orreciprocated. The polishing liquid supply nozzle 26 may be moved at aconstant rate (e.g., 50 mm/s) or at a varying rate. The polishing liquidsupply nozzle 26 may be combined with a liquid rate control mechanismfor changing a rate of the polishing liquid that is supplied from thepolishing liquid supply port 57 while the polishing liquid supply nozzle26 is in motion. A range that is scanned by the polishing liquid supplyport 57 should preferably be kept within a radius of the polishing table22 and cover a diameter of the semiconductor wafer being polished.

In this embodiment shown in FIG. 1, the polishing liquid supply nozzle26 extends in the radial direction of the polishing table 22. However,as shown in FIG. 9, the polishing liquid supply nozzle 26 may beinclined a certain angle ranging from 0° to 90° to the radial directionof the polishing table 22.

According to a CMP process, a semiconductor wafer is normally polishedby chemical mechanical action of a polishing liquid that is retained ona polishing pad. Heretofore, an ability of the polishing pad to retainthe polishing liquid is so small that most of the polishing liquidsupplied to the polishing pad is not consumed but discharged from thepolishing pad. Since the polishing liquid is highly expensive andgreatly affects polishing cost, it is necessary to increase a workingefficiency of the polishing liquid for reducing the polishing cost.

In a polishing process where polishing pressure is low (at most 6.89 kPa(1 psi)) and a relative speed between a semiconductor wafer and apolishing surface is high (at least 2 m/s), when a film of a polishingliquid supplied to the polishing surface is of an increased thickness,slippage occurs between the semiconductor wafer and the polishingsurface due to hydroplaning. Such a phenomenon manifests itselfparticularly if the polishing surface is supplied with the polishingliquid irregularly, for example, when the polishing surface hasconcentric grooves of small cross section defined therein or thepolishing liquid is supplied to the polishing surface from a singlepoint to a center of the polishing surface. When the hydroplaningphenomenon occurs, as no polishing pressure acts between thesemiconductor wafer and the polishing surface, a polishing rate islowered. If the polishing liquid is positively discharged from thepolishing surface, on the other hand, then an amount of the polishingliquid retained on the polishing surface is reduced, resulting in areduction in the polishing rate and working efficiency of the polishingliquid. Therefore, there has been a demand for retaining an appropriateamount of polishing liquid on the polishing surface to form a uniformfilm of polishing liquid on the polishing surface.

To meet such a demand, according to this embodiment, the polishing pad52 has grooves defined in a surface thereof, with each of the grooveshaving a cross-sectional area of at least 0.38 mm². FIG. 10 shows thepolishing pad 52 in perspective, and FIG. 11 shows the polishing pad 52in an enlarged vertical cross section. As shown in FIG. 10, thepolishing pad 52 has a plurality of concentric grooves 90 defined in anupper surface thereof and spaced at a pitch P₁ (see FIG. 11) of 2 mm,for example. According to an example shown in FIG. 11, each of thegrooves 90 has a width W₁ of 0.5 mm, a depth D₁ of 0.76 mm, and across-sectional area of 0.38 mm². The depth of each of the grooves 90may be greater than a depth of the conventional grooves, e.g., may be atleast 1 mm.

As shown in FIG. 12, the polishing pad 52 may further have straightnarrow slots 92 defined therein that interconnect adjacent ones of theconcentric grooves 90. The narrow slots 92 are effective to makepolishing liquid resistant to centrifugal forces. The narrow slots 92should preferably be inclined a certain angle α, e.g., 30°, relative toa circumferential direction of the polishing pad 52. Preferably,adjacent ones of the narrow slots 92 are spaced from each other by apitch P₂ of 2 mm. Each of the narrow slots 92 should preferably have awidth that is about 30% of the width of the grooves 90.

Though the polishing pad 52 has concentric grooves 90 in thisembodiment, the polishing pad 52 may have grooves of other shapes. Forexample, the polishing pad 52 may have spiral grooves defined in theupper surface thereof and each having a cross-sectional area that is thesame as the cross-sectional area of the concentric grooves 90. If thespiral grooves are inclined a certain angle, e.g., 45°, relative to adirection of a normal to the circumferential direction of the polishingpad 52, then polishing liquid can be discharged from the polishing pad52 under certain centrifugal forces.

The polishing pad 52 may have a plurality of holes defined in thesurface thereof, each having an opening area of at least 2.98 mm² and adiameter of at least 1.95 mm, instead of or in addition to theabove-described grooves 90. The holes having such a large opening area,which are defined in the surface of the polishing pad 52, are effectiveto increase an amount of polishing liquid retained by the polishingsurface and a working efficiency of the polishing liquid. The openingarea of each of these holes should preferably be at least 3.14 mm² (adiameter of at least 2 mm), or more preferably be at least 19.63 mm² (adiameter of at least 5 mm). The holes may be circular or elliptical inshape, and may be arranged in a concentric, staggered, or grid pattern.

The CMP process mainly comprises (1) a main polishing process forpressing a semiconductor wafer against a polishing pad and polishing thesemiconductor wafer while supplying a slurry to the polishing pad, and(2) a water polishing process for polishing (cleaning) the semiconductorwafer with water after the semiconductor wafer is polished by theslurry. In the main polishing process (1), an excessive film material ona surface of the semiconductor wafer is polished off. In the waterpolishing process (2), slurry deposits and debris produced in the mainpolishing process are washed off the surface of the semiconductor wafer.

As described above, as interconnects formed on semiconductor wafersbecome finer, insulating films of higher insulating ability arerequired. Porous low-k materials are known as candidates for materialsof such insulating films of higher insulating ability. However, porouslow-k materials are of very low mechanical strength. In view of this,polishing pressure applied in conventional CMP apparatus has been in therange from 13.79 to 344.47 kPa (2 to 5 psi). The polishing pressure willbe required to be at most 13.79 kPa (2 psi), or at most 6.89 kPa (1psi), in future.

Semiconductor wafers having low-k materials need to be polished under alow polishing pressure of 3.45 kPa (0.5 psi), for example. Both the mainpolishing process and the water polishing process are required to beperformed under a low polishing pressure. However, if the waterpolishing process is performed under a low polishing pressure, thendeposits such as slurry cannot fully be removed from the semiconductorwafer, but may possibly remain unremoved on the semiconductor wafer.

According to this embodiment, the water polishing process is performedas follows: After the main polishing process has been performed on asemiconductor wafer under a low polishing pressure, the semiconductorwafer is pressed against the polishing pad 52 under a pressure which isequal to or lower than the polishing pressure exerted in the mainpolishing process, and the polishing table 22 is rotated at a linearvelocity of at least 1.5 m/s, preferably at least 2 m/s, or morepreferably at least 3 m/s. Pure water (DIW) is supplied at a flow rateof 1 l/min. to the polishing pad 52 to polish the semiconductor waferwith water. In this manner, a surface of the semiconductor wafer thathas been polished under the low polishing pressure can be cleanedappropriately. Alternatively, the semiconductor wafer may be cleanedwith a chemical solution such as a citric acid solution which is able toaccelerate removal of slurry deposits and debris from the semiconductorwafer, rather than pure water (DIW). A period of time of a normalcleaning process may be prolonged from 10 sec. to 20 sec. to removeslurry deposits and debris from the semiconductor wafer. However, sincesuch a prolonged cleaning process lowers throughput, the water polishingprocess or chemical solution cleaning process described above, performedon the semiconductor wafer while in high-speed rotation, is morepreferable.

In the above-described embodiment, the polishing liquid is supplied fromthe polishing liquid supply port 57 at the distal end of the polishingliquid supply nozzle 26. Polishing liquid supply nozzles of otherdesigns may be employed. For example, as shown in FIG. 13, a polishingliquid supply nozzle 26 a may comprise a disk 100 having a polishingliquid supply port 57 and an arm 102 on which the disk 100 is mounted.The arm 102 may not be pivoted and only the disk 100 may be rotatedwhile supplying the polishing liquid from the polishing liquid supplyport 57, or the arm 102 may be pivoted and the disk 100 may be rotatedwhile supplying the polishing liquid from the polishing liquid supplyport 57. Alternatively, the arm 102 may be moved linearly. A movingspeed of the polishing liquid supply port 57, i.e., a moving speed ofthe arm 102 and/or a rotational speed of the disk 100 may be variedwhile polishing liquid supply nozzle 26 a is in operation. The polishingliquid supply nozzle 26 a may be combined with a liquid rate controlmechanism for changing a rate of polishing liquid that is supplied fromthe polishing liquid supply port 57 while the polishing liquid supplynozzle 26 a is in motion.

In FIG. 14, a polishing liquid supply nozzle 26 b may have a pluralityof polishing liquid supply ports 57. The polishing liquid supply nozzle26 b may be pivoted, linearly moved, rotated, swung, or reciprocated. Amoving speed of the polishing liquid supply nozzle 26 b may be variedwhile the polishing liquid supply nozzle 26 b is in motion. Thepolishing liquid supply nozzle 26 b may be combined with a liquid ratecontrol mechanism for individually controlling a rate of the polishingliquid that is supplied from each of the polishing liquid supply ports57 while the polishing liquid supply nozzle 26 b is in motion. Thepolishing liquid supply ports 57 may have different diameters. Forexample, the polishing liquid supply ports 57 may have progressivelydecreasing diameters in a radially inward direction of the polishingtable 22. In FIG. 14, the polishing liquid supply nozzle 26 b extends ina radial direction of the polishing table 22. However, as shown in FIG.15, the polishing liquid supply nozzle 26 b may be inclined a certainangle ranging from 0° to 45° relative to the radial direction of thepolishing table 22.

Rather than moving the polishing liquid supply nozzle, the polishingliquid supply port may be moved in the polishing liquid supply nozzle.For example, as shown in FIG. 16, a polishing liquid supply nozzle 26 chas a polishing liquid supply nozzle 57 a movable linearly therein.Alternatively, the polishing liquid supply nozzle 57 a may be pivoted,rotated, swung, or reciprocated. The polishing liquid supply nozzle 26 cmay not be pivoted and only the polishing liquid supply nozzle 57 a maybe moved while supplying polishing liquid. Alternatively, the polishingliquid supply nozzle 26 c may be pivoted and the polishing liquid supplynozzle 57 a may be moved while supplying the polishing liquid. A movingspeed of the polishing liquid supply nozzle 57 a may be varied while thepolishing liquid supply nozzle 57 a is in motion. The polishing liquidsupply nozzle 26 c may be combined with a liquid rate control mechanismfor changing a rate of the polishing liquid that is supplied from thepolishing liquid supply port 57 a while the polishing liquid supplynozzle 26 c is in motion. As shown in FIG. 17, a plurality of polishingliquid supply nozzles 26 c, each shown in FIG. 16, may be combined witheach other.

In FIG. 18, a polishing liquid supply nozzle 26 d comprises a disk 100having a plurality of polishing liquid supply ports 57 and an arm 102 onwhich the disk 100 is mounted. The arm 102 may not be pivoted and onlythe disk 100 may be rotated while supplying polishing liquid from thepolishing liquid supply ports 57, or the arm 102 may be pivoted and thedisk 100 may be rotated while supplying the polishing liquid from thepolishing liquid supply ports 57. Alternatively, the arm 102 may bemoved linearly. A moving speed of the polishing liquid supply ports 57,i.e., a moving speed of the arm 102 and/or a rotational speed of thedisk 100 may be varied while the polishing liquid supply nozzle 26 d isin operation. The polishing liquid supply nozzle 26 d may be combinedwith a liquid rate control mechanism for individually controlling a rateof the polishing liquid that is supplied from each of the polishingliquid supply ports 57 while the polishing liquid supply nozzle 26 d isin motion. The polishing liquid supply ports 57 may have differentdiameters. For example, the polishing liquid supply ports 57 may haveprogressively decreasing diameters in a radially inward direction of thepolishing table 22. According to an example shown in FIG. 18, thepolishing liquid supply ports 57 are positioned on one circle. However,the polishing liquid supply ports 57 may be positioned on a plurality ofconcentric circles or a single straight line or a plurality of straightlines.

In FIG. 19, a polishing liquid supply nozzle 26 e comprises a hollowroll 104 having a plurality of polishing liquid supply ports 57 definedin its wall. The roll 104 is rotatable about an axis parallel to thesurface of the polishing table 22. The polishing liquid supply ports 57may be arranged in a linear pattern, a spiral pattern, or a randompattern. Polishing liquid may be supplied from the polishing liquidsupply ports 57 while the roll 104 is being rotated or while the roll104 is being pivoted and rotated. A moving speed of the polishing liquidsupply ports 57, i.e., a rotational speed of the roll 104 and/or apivoting speed of the roll 104, may be changed while the polishingliquid supply nozzle 26 e is in operation. The polishing liquid supplynozzle 26 e may be combined with a liquid rate control mechanism forindividually controlling a rate of the polishing liquid that is suppliedfrom each of the polishing liquid supply ports 57 while the polishingliquid supply nozzle 26 e is in motion. The polishing liquid supplyports 57 may have different diameters. For example, the polishing liquidsupply ports 57 may have progressively decreasing diameters in aradially inward direction of the polishing table 22. The roll 104 may bedivided into a plurality of zones such that different polishing liquidsare supplied therefrom depending on a longitudinal direction of the roll104. According to an example shown in FIG. 19, the roll 104 of thepolishing liquid supply nozzle 26 e extends in a radial direction of thepolishing table 22. However, the roll 104 may be inclined a certainangle ranging from 0° to 45° relative to the radial direction of thepolishing table 22.

In FIG. 20, a polishing liquid supply nozzle 26 f comprises a hollowroll 104 having a spiral slit 106 defined in its wall. Polishing liquidmay be supplied from the spiral slit 106 while the roll 104 is beingrotated or while the roll 104 is being pivoted and rotated. A rotationalspeed of the roll 104 and/or the pivoting speed of the roll 104 may bechanged while the polishing liquid supply nozzle 26 f is in operation.The polishing liquid supply nozzle 26 f may be combined with a liquidrate control mechanism for controlling a rate of the polishing liquidthat is supplied from the slit 106. An opening width of the slit 106 maybe changed in location. For example, the opening width of the slit 106may progressively decrease in a radially inward direction of thepolishing table 22. The roll 104 may be divided into a plurality ofzones such that different polishing liquids are supplied therefromdepending on a longitudinal direction of the roll 104. According to anexample shown in FIG. 20, the roll 104 of the polishing liquid supplynozzle 26 f extends in a radial direction of the polishing table 22.However, the roll 104 may be inclined a certain angle ranging from 0° to45° relative to the radial direction of the polishing table 22.

According to the example shown in FIG. 20, the roll 104 has a spiralslit 106. However, the roll 104 may have a straight slit. FIG. 21 showsin perspective a polishing liquid supply nozzle 26 g having a straightslit defined therein, and FIG. 22 shows the polishing liquid supplynozzle 26 g in vertical cross section. As shown in FIG. 22, thepolishing liquid supply nozzle 26 g comprises a pressure holder 110having a pressure chamber 108 defined therein, and a slit body 114mounted in the pressure holder 110 and having a straight slit 112defined therein which extends downwardly from the pressure holder 110.The pressure holder 110 controls pressure of a polishing liquid Qsupplied to the pressure chamber 108 to adjust a flow rate of thepolishing liquid Q that is discharged from the slit 112. The slit 112 isstraight along the pressure holder 110, thereby allowing the polishingliquid Q to be discharged from the slit 112 uniformly therealong. Asshown in FIG. 23, the pressure chamber 108 may be divided into aplurality of compartments, and the compartments may be supplied with thepolishing liquid Q at different flow rates, so that the polishing liquidQ can be discharged from the slit 112 at different flow ratestherealong. The polishing liquid supply nozzle 26 g shown in FIGS. 21and 22 may be disposed along a radial direction of the polishing table22, or may be inclined a certain angle ranging from 0° to 45° relativeto the radial direction of the polishing table 22.

A polishing liquid supply nozzle 26 h shown in FIG. 24 may be employedto distribute polishing liquid supplied to the polishing pad 52. Thepolishing liquid supply nozzle 26 h has a fan-shaped distribution plate(distribution skirt) 116 for distributing polishing liquid Q ejectedfrom polishing liquid supply port 57. According to this polishing liquidsupply nozzle 26 h, while the polishing liquid Q ejected from thepolishing liquid supply port 57 is flowing on the distribution skirt116, the polishing liquid Q is distributed in different directions andsupplied to the polishing pad 52. The distribution skirt 116 may havegrooves or resistive members for limiting flow of the polishing liquidQ. The distribution skirt 116 may have a roughened surface to giveresistance to the flow of the polishing liquid Q flowing thereon. Thedistribution skirt 116 should preferably be made of a chemical-resistantmaterial such as fluororesin or the like. As shown in FIG. 25, thepolishing liquid supply nozzle 26 g shown in FIG. 21 may be combinedwith a distribution skirt 116.

A polishing liquid supply nozzle 26 i shown in FIG. 26 may be employedto distribute polishing liquid supplied to the polishing pad 52. Thepolishing liquid supply nozzle 26 i comprises a disk-shaped nozzle body118 and a distribution plate 120 mounted on a lower surface of thenozzle body 118. The polishing liquid is supplied to the polishing pad52 through central through holes (not shown) defined in the nozzle body118 and the distribution plate 120. The distribution plate 120 has alower surface made of a resistive material. According to this polishingliquid supply nozzle 26 i, the polishing liquid supplied from thepolishing liquid supply port 57 is distributed in many directions by alower surface of the distribution plate 120 and applied to the polishingpad 52. The distribution plate 120 should preferably be made of achemical-resistant material such as fluororesin or the like.

FIG. 27 shows a distribution plate (contact member) 122 disposeddownstream of polishing liquid supply nozzle 26 with respect to adirection in which the polishing table 22 rotates, and brought intocontact with the polishing pad 52 for distributing polishing liquid Qsupplied to the polishing pad 52. The distribution plate 122 distributesthe polishing liquid Q supplied from the polishing liquid supply nozzle26 in a radial direction of the polishing table 22, thereby uniformizingdistribution of the polishing liquid Q on the polishing pad 52. Thedistribution plate 122 should preferably be made of a wear-resistantelastic material such as fluororesin or the like. The distribution plate122 may extend in a radial direction of the polishing table 22 or may beinclined a certain angle ranging from 0° to 45° relative to the radialdirection of the polishing table 22. The distribution plate 122 may beheld at rest, or may be pivoted, moved linearly, rotated, swung, orreciprocated. A moving speed of the distribution plate 122 may be variedwhile it is in motion. As shown in FIG. 28, the distribution plate 122may have a plurality of slits 124 to distribute the polishing liquid Qsupplied from the polishing liquid supply nozzle 26. Dimensions, e.g.,width, height, and pitch, of the slits 124 should preferably beadjustable by a shutter or the like.

If polishing liquid supply devices shown in FIGS. 9 and 13 through 28are employed, then the polishing pad 52 should preferably have aplurality of radially divided regions, such as the polishing pad withconcentric grooves, as shown in FIG. 10. The polishing pad 52 with theradially divided regions allows polishing liquid to be efficientlysupplied to a surface being polished of a semiconductor wafer whileholding the polishing liquid in the radially divided regions, ratherthan mixing the polishing liquid on the polishing pad 52.

As shown in FIG. 29, a conventional CMP apparatus 500 with a pluralityof polishing liquid supply ports is combined with a high-rate polishingliquid circulation system 502, which is disposed outside of the CMPapparatus 500, for circulating a polishing liquid at a high rate. Asingle polishing liquid supply line 504 is connected from the CMPapparatus 500 to the polishing liquid circulation system 502. In the CMPapparatus 500, the polishing liquid supply line 504 is branched into aplurality of lines 506 connected to respective polishing liquid supplyports. Depending on a shape of polishing liquid supply nozzles,polishing liquid tends to be supplied from the polishing liquid supplyports at different rates, and the polishing liquid supply nozzles needto be adjusted or combined with valves for supplying the polishingliquid uniformly to the polishing pad.

According to this embodiment, as shown in FIG. 30, a polishing apparatus200 is combined with a high-rate polishing liquid circulation system 210which comprises a polishing liquid tank 202, a pressure pump 204, aback-pressure valve 206, and a pipe 208. A plurality of polishing liquidsupply lines 212 extend from respective polishing liquid supply ports57, and are connected directly to the pipe 208 of the high-ratepolishing liquid circulation system 210. The arrangement shown in FIG.30 makes it possible to uniformly supply polishing liquid to asemiconductor wafer to be polished for thereby improving a polishingrate and greatly increasing in-plane uniformity of the polishing rate.

As shown in FIG. 30, the polishing liquid supply lines 212 haverespective fluid pressure valves 214 as flow regulating valves forregulating flow rates of the polishing liquid supplied from thepolishing liquid supply ports 57. As shown in FIGS. 31A and 31B, each ofthe fluid pressure valves 214 has a pipe compression section 216 forreducing a diameter of a flexible pipe 212 a of one of the polishingliquid supply lines 212 under a fluid pressure. The pipe compressionsection 216 is disposed around the pipe 212 a. As shown in FIG. 31B,when the pipe 212 a is compressed by the pipe compression section 216under the fluid pressure, a flow rate of the polishing liquid Q flowingthrough the pipe 212 a is reduced. Since the pipe 212 a is compressed bythe pipe compression section 216 under the fluid pressure, the pipe 212a is prevented from being unduly worn.

The retainer ring of the top ring controls a polishing profile of aworkpiece (semiconductor wafer) to be polished by (1) holding an outercircumferential edge of the workpiece and (2) pressing itself against apolishing surface (polishing pad). If a polishing liquid for forming acopper complex having a low mechanical strength is used under a lowpolishing surface pressure, as described above, then excessivelypressing the retainer ring against the polishing surface tends to limitsupply of the polishing liquid to a surface of the workpiece to bepolished. Therefore, load applied to press the retainer ring against thepolishing surface should be as small as possible. However, if the loadapplied to press the retainer ring against the polishing surface is toosmall, the workpiece held by the retainer ring is liable to be displacedfrom the retainer ring. Therefore, there has been a demand forpreventing the workpiece from being displaced from the retainer ringeven when the load applied to press the retainer ring against thepolishing surface is small.

To meet such a demand, as shown in FIG. 32, a retainer ring 356, whichcomprises a presser 300 for pressing the polishing pad 52 to adjust astate of contact between the semiconductor wafer W and the polishing pad52, and a ring-shaped guide 302 for preventing the semiconductor wafer Wfrom being displaced from the top ring 24, may be employed. The guide302 is positioned radially inwardly of the presser 300 closely to thesemiconductor wafer W. According to this retainer ring 356, even ifpolishing pressure is low, the retainer ring 356 can control a polishingprofile of the semiconductor wafer W while preventing the semiconductorwafer W from being displaced from the top ring 24.

The guide 302 is vertically positionally adjustable by a screw or an aircylinder to adjust a height between the surface of the polishing pad 52and the guide 302. The guide 302 should preferably have a radial widthof at most 6 mm, and should preferably be made of a material having alow level of hardness.

In a CMP process for planarizing copper damascene interconnects forsemiconductor device fabrication, a copper film is fully removed up to abarrier metal, leaving copper interconnects. As shown in FIGS. 33Athrough 33C, a process of removing the copper film up to the barriermetal comprises a first step (bulk copper polishing process, see FIGS.33A and 33B) of quickly removing most of an initial copper film 400 andreducing initial steps to leave a slight copper film 400 a, and a secondstep (copper clearing process, see FIGS. 33B and 33C) of fully removingremaining copper film 400 a to a barrier metal 402, leavinginterconnects 400 b.

In the bulk copper polishing process, an initial step is reduced(planarized) as much as possible and the copper film 400 a is leftuniformly in a film as thin as possible, for reducing a load on thecopper clearing process. For example, a thickness of the copper film 400a that remains after the bulk copper polishing process should be in arange from 100 to 150 nm, preferably at most 100 nm, or more preferablyat most 50 nm. Generally, as shown in FIG. 34A, the copper clearingprocess is performed under a reduced polishing pressure in order toreduce dishing 410 and erosion 412 after removal of the copper film.

The conventional CMP apparatus has determined a timing for processswitching based on information as to film thickness at a certainposition in a wafer plane. According to such a method, since the timingfor process switching is determined irrespective of a film thicknessdistribution during a polishing process, even if a polishing profile ischanged, process switching is performed when the film thickness at aposition being measured on a wafer reaches a predetermined value.

If a remaining copper film whose thickness is much larger than in theposition being measured is present in another position on the wafer,then, as shown in FIG. 34B, remaining copper films 414 may possiblyoccur after a next copper clearing process is ended. Conversely, if aremaining copper film whose thickness is much smaller than in theposition being measured is present in another position on the wafer,then dishing 410 and erosion 412 may possibly occur in such anotherposition, as shown in FIG. 34A.

The above problem can be avoided by the following process: A filmthickness distribution of a copper film upon transition from the bulkcopper polishing process to the copper clearing process is preset andstored in a memory. During the bulk copper polishing process performedon a semiconductor wafer, a film thickness distribution of a copper filmon the semiconductor wafer is acquired from the eddy-current sensor 58(see FIG. 2). According to a simulation software program, the presetfilm thickness distribution and the acquired film thickness distributionare instantaneously compared with each other, and polishing conditionsrequired to achieve the preset film thickness distribution aresimulated. Based on simulated polishing conditions, the top ring 24controls a polishing profile to achieve the preset film thicknessdistribution. For example, the top ring 24 increases a polishing ratefor an area where an amount of polishing is insufficient in the presentfilm thickness distribution. This polishing profile control thusperformed allows remaining copper film to have a uniform thickness orthe preset film thickness distribution immediately prior to the copperclearing process. When an actual film thickness distribution agrees withthe preset film thickness distribution, the bulk copper polishingprocess switches to the copper clearing process.

The above process makes it possible to achieve a finally desirable filmthickness distribution securely while monitoring an actual polishingconfiguration (film thickness distribution). Since the bulk copperpolishing process can switch to the copper clearing process at a desiredfilm thickness distribution at all times, the copper clearing processcan be started under constant conditions at all times without beingaffected by process variations of the bulk copper polishing process,i.e., variations of a polishing rate and polishing profile. Accordingly,any undue load on a next copper clearing process can be minimized. Thisprocess contributes to not only a reduction in the dishing 410 and theerosion 412 after the copper clearing process, but also a reduction in aperiod of time consumed by the copper clearing process, i.e., areduction in excessive polishing time, an increase in productivity, anda reduction in polishing cost.

After a conductive film on a semiconductor wafer is polished in aprocess of forming interconnects, any defects that are present, e.g.,residues 414 of the conductive film, scratches, and pits 416 (see FIGS.34A and 34B) affect not only a sequential process of forminginterconnects, but also electric characteristics of electric circuitsthat are finally formed on a semiconductor wafer. Consequently, it isdesirable to eliminate these defects at an end of the polishing process.

According to the CMP process, the residues 414 of the conductive filmmay be eliminated by overpolishing the semiconductor wafer by athickness greater than the thickness of the initial film. Generally,overpolishing the semiconductor wafer for a long period of time tends tocause dishing 410 and erosion 412 in interconnect areas of thesemiconductor wafer, as shown in FIG. 34A. In addition, scratches andpits 416 are inevitable because of mechanical polishing action on thesemiconductor wafer.

Generally, since remaining conductive films 414 cannot be removed byordinary polishing, they need to be removed by overpolishing. However,overpolishing tends to cause dishing 410, erosion, scratches, and pits416 on the semiconductor wafer, as described above. In order toeliminate these defects, the bulk copper polishing process is performedby CMP, and the subsequent copper clearing process by CMP is stoppedwhen the remaining copper film reaches a thickness of at most 50 nm.Thereafter, the copper clearing process is performed by a chemicaletching process to remove the copper film. The copper clearing processperformed by a chemical etching process free of a mechanical polishingaction can polish the copper film without causing defects.

An etchant used in the chemical etching process may be an acid such assulfuric acid, nitric acid, halogen acid (particularly, hydrofluoricacid or hydrochloric acid), an alkali such as ammonia water, or amixture of an oxidizing agent such as hydrogen peroxide and an acid suchas hydrogen fluoride or sulfuric acid. In the bulk copper polishingprocess, it is preferable to measure a thickness of a conductive thinfilm, and when this measured thickness reaches a predetermined thicknesssuch as at most 100 nm, the bulk copper polishing process shouldpreferably switch to the copper clearing process. The thickness of sucha conductive thin film may be measured by at least one of an opticalsensor for applying light to the conductive thin film to measure thefilm thickness, an eddy-current sensor for detecting an eddy currentproduced in the conductive thin film to measure the film thickness (seeFIG. 2), a torque sensor for detecting a running torque of the polishingtable 22 to measure the film thickness, and an ultrasonic sensor forapplying ultrasonic energy to the conductive thin film to measure thefilm thickness.

The above chemical etching process is not limited to the bulk copperpolishing process for forming a thin copper film with the CMP apparatus,but may be combined with other processes. Specifically, after variousprocesses for forming a flat conductive thin film on a substrate, theconductive thin film may be removed by the chemical etching process.

For example, after a thin film is formed by an electrolytic polishingprocess, this formed thin film may be removed by the chemical etchingprocess. The electrolytic polishing process is effective to reducescratches and pits 416 because it does not involve a mechanical action.However, if a conductive film that fails to make an electric connection,e.g., a slight remaining conductive film on an insulating material,occurs, then the electrolytic polishing process is unable to remove sucha remaining conductive film. However, a flat conductive thin film thatis formed by the electrolytic polishing process can be removed by thechemical etching process which requires no electric connection, withoutcausing defects. The electrolytic polishing process is not limited toany particular type. For example, an electrolytic polishing processusing an ion exchanger or an electrolytic polishing process using no ionexchanger may be employed. The electrolytic polishing process shouldpreferably be performed with use of ultrapure water, pure water, or aliquid or an electrolytic solution having an electric conductivity ofnot more than 500 μS/cm. For example, the electrolytic polishing processmay be performed by an electrolytic processing apparatus as disclosed inJapanese laid-open patent publication No. 2003-145354, for example.

After a thin film is formed by a flat plating process, this formed thinfilm may be removed by the chemical etching process. Formation andremoval of a copper film (Cu) has been described above. However, thepresent invention is applied to formation and removal of other films.For example, after a conductive thin film containing at least one of Ta,TaN, WN, TiN, and Ru is formed, this formed thin film may be removed bythe chemical etching process.

Example

A polishing apparatus shown in FIG. 35 was used to polish asemiconductor wafer with polishing liquid supply nozzle 26 beingactually swung in a polishing process. FIG. 36A is a graph showing apolishing rate of the semiconductor wafer which was polished by thepolishing apparatus shown in FIG. 35. FIG. 36B is a graph showing apolishing rate of a semiconductor wafer which was polished by thepolishing apparatus shown in FIG. 35 with the polishing liquid supplynozzle 26 being not swung in the polishing process. A comparison betweenthese graphs indicates that in-plane uniformity of a polishing rate ofthe semiconductor wafer was higher when the polishing liquid supplynozzle 26 was swung in the polishing process.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made therein without departing from thescope of the appended claims.

1-70. (canceled)
 71. A method for polishing a workpiece, the methodcomprising the steps of: polishing the workpiece to remove a substantialportion of a first film formed on the workpiece by pressing theworkpiece against a polishing surface while supplying a polishing liquidto the polishing surface from a polishing liquid nozzle in a first-stagepolishing; polishing the workpiece to remove a remaining portion of thefirst film until a second film on the workpiece is exposed in asecond-stage polishing, leaving an interconnect area; presetting a filmthickness distribution for the first film upon transition from saidfirst-stage polishing to said second-stage polishing; measuring athickness of said first film with a film thickness sensor in saidfirst-stage polishing to acquire a film thickness distribution of saidfirst film; and adjusting polishing conditions in said first-stagepolishing to equalize the acquired film thickness distribution of saidfirst film to the preset film thickness distribution for the first film.72. A method according to claim 71, wherein said first-stage polishingis switched to said second-stage polishing when the acquired filmthickness distribution of said first film is equalized to the presetfilm thickness distribution for the first film.
 73. A method accordingto claim 71, wherein said adjusting polishing conditions in saidfirst-stage polishing is carried out by adjusting polishing liquidsupply conditions for supplying the polishing liquid to the polishingsurface.
 74. A method according to claim 71, wherein said film thicknesssensor is an eddy current sensor.
 75. A method according to claim 71,wherein said film thickness sensor is an optical sensor.
 76. A methodaccording to claim 73, wherein said adjusting polishing liquid supplycondition is carried out by varying a moving speed of said polishingliquid supply nozzle while said polishing liquid supply nozzle is beingmoved.
 77. A method according to claim 76, wherein said polishing liquidsupply nozzle is moved such that said polishing liquid supply nozzlemoves at least one of a pivoting motion, a reciprocating motion, arotational motion, and a liner motion.
 78. A method according to claim76, wherein said polishing liquid supply nozzle has a plurality ofpolishing liquid supply ports.
 79. A method according to claim 76,wherein said polishing liquid supply nozzle extends in a radialdirection of said polishing surface.
 80. A method according to claim 76,wherein said polishing liquid supply nozzle is inclined a predeterminedangle to a radial direction of said polishing surface.
 81. A methodaccording to claim 73, wherein said adjusting polishing liquid supplycondition is carried out by controlling a rate of the polishing liquidsupplied from said polishing liquid supply nozzle to said polishingsurface.
 82. A method according to claim 79, wherein said polishingliquid supply nozzle has a plurality of polishing liquid supply portsand rates of the polishing liquid supplied from said polishing liquidsupply ports to said polishing surface are individually controlled. 83.A method for polishing a workpiece, the method comprising: polishing theworkpiece to remove a film formed on the workpiece by pressing theworkpiece against a polishing surface while supplying a polishing liquidto the polishing surface from a polishing liquid nozzle; presetting afilm thickness distribution for the film; measuring a thickness of thefilm with a film thickness sensor to acquire a film thicknessdistribution of the film during polishing of the film; simulatingpolishing conditions to achieve the preset film thickness distributionfor the film by comparing the acquired film thickness distribution ofthe film and the preset film thickness distribution for the film witheach other; and adjusting polishing condition of the film based on thesimulated polishing conditions.
 84. A method according to claim 83,wherein said adjusting polishing condition is carried out by adjustingpolishing liquid supply conditions for supplying the polishing liquid tothe polishing surface.
 85. A method according to claim 83, wherein saidfilm thickness sensor is an eddy current sensor.
 86. A method accordingto claim 83, wherein said film thickness sensor is an optical sensor.87. A method according to claim 84, wherein said adjusting polishingliquid supply condition is carried out by varying a moving speed of saidpolishing liquid supply nozzle while said polishing liquid supply nozzleis being moved.
 88. A method according to claim 87, wherein saidpolishing liquid supply nozzle is moved such that said polishing liquidsupply nozzle moves in at least one of a pivoting motion, areciprocating motion, a rotational motion, and a linear motion.
 89. Amethod according to claim 87, wherein said polishing liquid supplynozzle has a plurality of polishing liquid supply ports.
 90. A methodaccording to claim 87, wherein said polishing liquid supply nozzleextends in a radial direction of said polishing surface.
 91. A methodaccording to claim 87, wherein said polishing liquid supply nozzle isinclined a predetermined angle to a radial direction of said polishingsurface.
 92. A method according to claim 84, wherein said adjustingpolishing liquid supply condition is carried out by controlling a rateof the polishing liquid supplied from said polishing liquid supplynozzle to said polishing surface.
 93. A method according to claim 92,wherein said polishing liquid supply nozzle has a plurality of polishingliquid supply ports and rates of the polishing liquid supplied from saidpolishing liquid supply ports to said polishing surface are individuallycontrolled.